1. Field of the Invention
The present invention relates to wireless sensor networks. More particularly, the present invention relates to a communication method and apparatus using a received signal strength indicator (RSSI) of another node in a wireless sensor network.
2. Description of the Related Art
In recent years, wireless sensor network technology has been put to practical use in a variety of industrial fields. In particular, the steady growth of the Internet, combined the development of low-priced sensors, the changing environment of internal standards, etc., have been catalysts in the development of wireless sensor technology. Sensor networks detect information through sensors and processes the detected information, which in turn makes provides a variety of information for the application of science and technology to useful applications in both the household, in industry, and for personal enjoyment. Sensor networks refer to wireless networks that serve to implement ubiquitous computing and include a plurality of sensors that are light weight and energy efficient.
The conventional study of sensor networks has progressed in some areas but has been static with regard to studying the mobility of respective nodes in the sensor network and ways to benefit from such movement. Therefore, a MAC protocol applied to the conventional sensor network does take into consideration the mobility of any of the nodes.
On the contrary, sensor networks have characteristics where each network includes a plurality of sensors, and each of the sensor nodes has restricted power and computing capability, and the topology of the sensor network can be easily changed because sensor nodes are inserted into and removed from the network frequently, as some of the sensor nodes are moved.
FIG. 1A and FIG. 1B are views illustrating a topology of a conventional sensor network.
As shown in FIG. 1A, node 1 has its adjacent nodes 2˜5. Node 1 includes nodes 2˜5 in its adjacent node list and manages them. Managing the adjacent nodes includes detecting whether or not their power supply is turned on or off. As can be seen, node 6 is outside of the network.
Now referring to FIG. 1B, which may be considered a subsequent “snap shot” in time as compared with FIG. 1A, node 1 transmits data to node 3. However, at a the point in time that node 1 transmits data to node 3, node 3 moves out of the transmission range of node 1, and node 6 moves thereinto. In that case, although node 1 had to insert node 6 into its adjacent node list and to remove node 3 therefrom, it still maintains and manages nodes 2˜5 therein. Since node 3 is included in the adjacent node list of node 1, node 1 attempts to re-transmit data to node 3 by a predetermined frequency, which causes an increase in unnecessary traffic.